1. Field of the Invention
This invention relates to manholes for sewer systems and more particularly, to a watertight manhole insert which is designed to seal the manhole immediately beneath a manhole cover to prevent flooding of the sewer system. In a preferred embodiment of the invention the manhole insert is characterized by a bowl-shaped dish having a rounded or cupped bottom provided with a pressure relief valve and an optional vacuum relief valve, and having vertical sides which are terminated by an outwardly-projecting rim adapted for seating on a shoulder formed in the manhole beneath the manhole cover. In a most preferred embodiment of the invention the outwardly-extending rim is sandwiched between a ribbed seal, the upper flat element of which seal receives the manhole cover and the ribbed bottom element resting on the shoulder shaped in the manhole, to prevent, or at least minimize, the flow of water from ground level around the manhole cover and through the manhole, into the sewer system. The rounded, dish-shaped bottom of the manhole insert is provided with spaced ribs for strength and both ends of a lift strap may be attached to the insert bottom, in order to facilitate lifting and removing the manhole insert from a mounted position in the manhole. In another preferred embodiment of the invention one or more side ribs or stiffeners may be provided in the upward-standing side wall extending from the dish of the manhole insert, to provide additional side wall strength. The pressure relief valve is designed to relieve pressure which may be generated in the sewerage system served by the manhole, while the optional vacuum relief valve operates to relieve any vacuum which may develop in the sewerage system.
One of the problems which is associated with sewerage systems is that of flooding during periods of high water due to prolonged or heavy rainfall. This problem is intensified in both urban and surburban areas where increased construction activity has resulted in large quantities of concrete being poured to construct parking lots, as well as foundations and other structures. This increase in non-permeable construction material reduces the amount of surface area which is available to absorb rainfall and increases the flow of water in storm drains and sewerage systems, as well as diversion canals, natural streams and other channels which must accept and dispose of the increased flow of water. These conditions of urban and suburban development result in flooding, under circumstances where the water exceeds the capacity of storm drain and sewerage systems, which systems are sized to receive a specified average flow of water. Moreover, it is customary to provide separate drainage systems for rainwater and sewage and flooding of the sewerage systems by rainwater runoff sometimes creates a contamination problem.
2. Description of the Prior Art
Various types of closures and covers, many of which are fitted with ventilating means, have been long known in the art. An early patent which details such a closure is the "Ventilating Vault Cover" detailed in U.S. Pat. No. 606,554, dated Jun. 28, 1898, to J. Jacobs. The ventilating vault cover is designed to close a vault opening in a watertight manner when in a closed position and vent the vault when in open configuration. U.S. Pat. No. 3,046,853, dated July 31, 1962, to C. Legendre, discloses a "Manhole Closure". The manhole closure includes a lid of one-piece construction which cooperates with a seat or manhole frame, also of one-piece construction, such that the two parts can be easily assembled for mounting in a manhole. A "Safety Replacement Cover for Catch Basins" is detailed in U.S. Pat. No. 2,576,353, dated Nov. 27, 1951, to O. W. Nelson. The cover detailed in this patent includes a dish-like, reticulate tray which is designed to provide adequate drainage into a catch basin and facilitates safety to prevent injury from stepping into the catch basin. A "Manhole Cover" is covered in U.S. Pat. No. 3,920,347, dated Nov. 18, 1975, to John T. Sauriol, et al. The manhole cover is constructed of a molded synthetic polymeric material and has a transversely intersecting structural rib network which is integrally joined with a top surface portion and encloses annular peripheral portions of the cover. The structural rib network is preferably dome-shaped, with the principal structural support disposed centrally of the cover at the apex of the dome. A "Drain Hole Seal With Bottom Bleeder" is detailed in U.S. Pat. No. 4,649,674, dated Mar. 17, 1987, to Craig S. Gaul, et al. The patent details a seal structure having a bottom bleeding feature such as a bottom bore and fitted with a flange to facilitate sealing engagement between a cover and a frame located around an access opening of the manhole. The structure includes a central portion which is downwardly depressed to avoid a path of spin of the cover. A "Watertight Manhole Insert" is set forth in U.S. Pat. No. 4,650,365, dated Mar. 17, 1987, to Franklin D. Runnels. The manhole insert is designed to prevent rainwater from entering a sanitary sewer system through manholes which are closed by manhole covers. The insert includes a shallow, dish-shaped body portion and a mounting flange designed to rest upon the supporting flange of a manhole frame. A recess is formed in the bottom of the body portion and includes a valve for releasing pressure which accumulates in the manhole beneath the insert. The valve is shielded to prevent damage by a manhole cover sliding across the insert. Additionally, the valve can be used as a handle to remove the insert from the manhole. The Runnels insert has also been modified in application to include a circumferential rib near the rim for stiffening purposes. A "Manhole Closure Assembly" is detailed in U.S. Pat. No. 4,067,659, dated Jan. 10, 1978, to Samuel A. Campagna, Jr., et al. The assembly is designed to prevent accumulated storm water from entering into a manhole opening and includes a cover section having a downwardly-depressed central portion. A circular mounting flange extends outwardly from the depressed central portion and the flange is adapted to rest upon inwardly-directed manhole cover supporting flanges of the annular manhole frame. The cover section is depressed, such that the cover exceeds the path of spin when resting upon the supporting flange of the manhole frame. A valve is secured to the cover section for the purpose of relieving pressure inside the manhole when the sewer pressure exceeds a predetermined level.
It is an object of this invention to provide a new and improved manhole insert which is designed to close and substantially seal a manhole to prevent rainwater from flooding a sewerage system communicating with the manhole.
Another object of the invention is to provide a manhole insert which is molded, stamped or otherwise shaped from a selected metal or synthetic polymeric material into a dish-shaped, flanged bowl having upward-standing ribs in the dish section thereof for installation on a shoulder provided in a manhole beneath the manhole cover, in order to prevent, or at least reduce, the flow of rainwater into the manhole and the underlying disposal system.
A still further object of this invention is to provide a manhole insert having a dish-shaped bottom fitted with an upward-standing, substantially vertically-oriented side having at least one circumferential side rib for stiffening purposes and a flange or rim outwardly-extending from the side, which rim engages the shoulder of a manhole located beneath the manhole cover to retard water from flowing into the manhole and the underlying sewer or drainage system.
Yet another object of the invention is to provide a manhole insert for retarding the flow of water into a sewerage system through a manhole, which insert is characterized by a dish-shaped closure having an outwardly-projecting flange or rim that is fitted with a locked-on rubber seal and further including upward-standing ribs spaced in the dish portion thereof, which manhole insert is located in the manhole beneath the manhole cover.
Still another object of this invention is to provide a new and improved manhole insert which includes a dish-shaped stopper or plug having a pressure relief valve and a vacuum relief valve mounted therein and further including an outwardly-extending rim fitted with a locked-on rubber seal, multiple upward-standing, spaced ribs provided in the bowl-shaped bottom of the insert and an optional lift strap attached to the bowl portion of the insert at both ends, for removing the insert from a manhole located beneath the manhole cover.
Another object of the invention is to provide a new and improved, ribbed manhole insert which is fitted with a locked-on rubber seal for mounting in the upper portion of a manhole beneath the manhole cover, which rubber seal includes a top element and a bottom element sandwiched on the manhole insert rim, wherein the top element is permanently attached to the bottom element at spaced intervals through holes or openings provided in the rim, in order to reduce or prevent the flow of water into an underlying sewerage system, control manhole odor and prevent the accumulation of dirt and trash in the manhole and the underlying sewer.